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Gunnlaugur Petur (G. Petur) Nielsen, MD

Associate Pathologist, Massachusetts General Hospital

Subspecialty Head, Bone and Soft Tissue Pathology

Associate Professor of Pathology, Harvard Medical School

Dr. Nielsen provides diagnostic and consultation services in the United States and internationally. He is director of the Electron Microscopy Lab in the Immunopathology Service.

Department of Pathology


  • Cancer Center
  • Sarcoma and Connective Tissue Oncology
  • Head & Neck Cancers
  • Chordoma
Clinical Interests
Bone and Soft Tissue Pathology
Electron Microscopy
Head and Neck Pathology
Frozen Section Pathology
Boston: Massachusetts General Hospital
Medical Education
MD, University of Iceland Faculty of Medicine
Residency, Massachusetts General Hospital
Residency, University of Iceland Faculty of Medicine
Board Certifications
Anatomic Pathology, American Board of Pathology
Pathology, American Board of Pathology
Foreign Languages
Patient Age Group
Accepting New Patients
Accepting New Patients


Dr. Nielsen has written extensively on neoplastic and non-neoplastic diseases and of bone and soft tissue. He is the co-author of several book chapters, has participated in writing a number of sections over the last few years for the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone, and co-authored Diagnostic Pathology: Bone. Dr. Nielsen is a regular speaker at national and international pathology and orthopedic courses.


Research interests include pathology and biology of bone and soft tissue tumors and the application of ancillary studies in the diagnosis of bone and soft tissue neoplasms. Dr. Nielsen is especially interested in chordoma research.  For more information about research concepts, co-authors, and to see a timeline, visit Dr. Nielsen's profile at the Harvard Clinical and Translational Science Center.


View my most recent publications at PubMed

Pathology Associates
55 Fruit Street
Boston, MA 02114-2696

Phone: 617-724-1469
Fax: 617-726-9312